In the 1950's it was revealed that prior to WW2, in 1937, Hitler used the Czechoslovak National Socialist Benes family to pass on a fake dossier to Stalin that the Gestapo had manufactured.  The manufactured documents claimed that Soviet General Tukhachevsky was colluding with Hitler to overthrow Stalin.  Stalin was duped by the fake documentation & had 7 of his ranking generals shot, a two year "purge" of his armed forces followed, decimating the best Soviet officer cadets and substantially weakening the Soviet army prior to WW2 and Hitler's onslaught in June 1941.